This is a guest post by Jamie L. Vernon, Ph.D., a research scientist and policy wonk, who encourages the scientific community to get engaged in the policy-making process

While many of us were howling about global warming over the last decade, Earth’s surface temperature actually failed to significantly increase. Yes, I said it. Global surface temperature showed little warming between 1998 and 2008. But, don’t go and broadcast the demise of the global warming movement quite yet. The reasons for the cooling trend are not encouraging. In fact, they are quite threatening. And, if environmentalists have their way (and I think they should), global warming will reemerge and may do so at an alarming rate.

A team of researchers led by Harvard professor James Stock have determined that gases resulting from human activities in conjunction with natural variables can explain the “1999-2008 hiatus in warming.” Using published statistical models, they were able to demonstrate that a rapid increase in coal consumption in Asia likely generates sufficient sulfur emissions to reduce global surface temperatures. They write,

We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations.

In other words, despite the influence of other natural variables, sulfur dioxide is the major driver of recent temperature fluctuations. Sulfur dioxide is a natural by-product of burning coal. Accumulation of sulfur dioxide aerosols in the atmosphere reflects the sun’s rays leading to a cooling effect on global surface temperatures. Because emissions from human activities greatly exceed natural production, increased dependence upon coal-based energy production can lead to sulfur dioxide-driven cooling effects that counteract the warming caused by increasing carbon dioxide.

The authors cite China’s growing dependence on coal as an energy source to explain the increase in sulfur emissions. From 2003 to 2007, Chinese coal consumption more than doubled. Prior to that, it took 22 years for China to double its coal usage. Whereas global coal consumption increased by 27% from 1980 to 2002, the recent Chinese growth rate which occurs over a 4 year period (5 times the previous rate) represents 77% of the 26% rise in global coal consumption.

So why not rely on sulfur dioxide as a geoengineering tactic for regulating global warming?

The sulfur dioxide produced by these coal-fired power plants is a pollutant that contributes to the production of acid rain. Forests, crops, buildings, aquatic life and human health are all negatively impacted by acid rain. In 1963, motivated by the environmental movement, the U.S. Congress passed the Clean Air Act (CAA), which established standards for regulating pollutants such as sulfur dioxide. However, it took until 1990 for Congress to strengthen CAA enough to force the coal industry to significantly cut or trap sulfur emissions. This legislation successfully decreased sulfur dioxide emissions by 40% from 1990 levels. As a result, the reduction of sulfur dioxide emissions dramatically reduced the cooling effects associated with these gases. Thus, removing sulfur dioxide to protect crops, forests, wildlife and human health resulted in the warming trend observed between 1990 and 2002.

Given the negative effects of sulfur dioxide on the environment and human health, we should expect Chinese environmentalists to act to reduce these pollutants. Indeed, China has already made some moves in this direction. Subsequent temperature increases will very likely be more dramatic than those observed during the 1990’s, because the global community has done little to reduce the warming effects that will occur due to continual accumulation of carbon dioxide in the atmosphere.

For those who would like to use this as evidence against global warming, I invite you to closely examine the following graph from the paper described herein. You’ll notice that the window of time during which this temperature stabilization was observed occurs at the high end of a 100 year warming trend. The temporary cooling does not suggest that warming observed since 1910 has been reversed or that we shouldn’t expect additional warming in the future.

If you take a look at figure 1 in the paper, you’ll see the solar insolation drop is bigger than the sulfur forcing change over the last decade. (Orange and purple lines respectively.) Not that I’d read too much into that – understanding of solar effects as represented in computer models is poor – but it’s interesting how it is phrased in their abstract/conclusions.

A lot of computer models and indirect estimates, and telling us nothing we didn’t already know, but I’m not complaining.

@3 SocraticGadfly – You must remember that you are a regular reader of global warming science. Therefore, you are well-informed of the issues and debates. Some in the general public are not as informed so we must take opportunities like this one where new science has been published to inform the public of what is happening in climate science.
It’s not useful to attack others. I’d prefer to see you engage them and try to understand their reasons for disagreeing with climate science. Are they misinformed, ill-informed or simply confused? Attacking and insulting is of no benefit.
Jamie

Agreed on the benefit of attacking and insulting. And I also agree that education is a worthy aim, and I like articles with some scientific content – even if it’s old news.

I, also, was a bit confused by #1. I think the reason for it was that the paper seemed to be claiming that natural warming episodes were caused by volcanic sulfates, and somebody might assume therefore that sulfates generally cause warming, not cooling. (That’s a guess, because #1 didn’t explain.) If you look a little closer, you’ll see that the paper proposes lower levels of sulfates cause cooling, but very high levels use up the atmosphere’s capacity to clean up other pollutants, particularly certain greenhouse gases like methane, and these cause warming. They note a correlation between extreme volcanic activity and sudden warmings, like the start of the Medieval Warm Period. They don’t have much evidence, but it’s an interesting hypothesis.

Unlike the Kaufmann paper, which says nothing new, this one has introduced a genuinely novel idea (at least to me) by means of which past natural warmings like the MWP can be reclaimed by the AGW camp. Having spent years trying to prove the MWP didn’t exist or didn’t happen uniformly and failing, they now have a model in which the MWP was also caused by greenhouse gases, and hence the stronger and more coherent it was, the more sensitive the Earth must be to GHGs and hence the more alarmed we ought to be. A neat turnaround!

There is of course much still to argue about, and their mechanism sounds a bit speculative to me; but it seems to me a significant step for your side, and a more important paper than Kaufmann et al. We shall have to see how it goes – it’s early days yet.

Um.. I’m a non-avid reader of climate science like #1 but this article seems to be a little bit of lamp shading on the part of the scientists to try to explain away the 1999 to 2008 cooling trend (something that isn’t necessary because global warming has already been hit with a series of pits and valleys over the last hundred years, alongside mountains and cliff faces). What gets me about global warming is not the science. Not being a climate scientist, I don’t know if the science is accurate or not. Its the alarmist, ‘we-must-act-NOW’ salesmanship that serves to simultaneously cloud thinking of those who are listening and try to force action without consideration of the consequences.

On consequences, I’m a little more forgiving; I don’t believe that the consequences for a lot of actions can be foreseen. What it comes down to is that everything is part of a series of systems. When you change one object, other linked elements are impacted. It is impossible for enough data to be gathered to completely account for each possible consequence of a series of actions. Global warming is a consequence of the progress of human society. Improved living conditions and the reduction of real levels of poverty (as in, in America our poor have an obesity problem too) are the things that have caused global warming.

This is not an attempt to create a false dichotomy of choosing between poverty reduction or prevention of global warming (although to really reverse trends of global warming might bankrupt the wealthy nations). This is an observation that there are consequences to the consequence mitigation strategies which I find objectionable because they hurt the way humans are living. What I haven’t heard yet is a way to improve our lives while simultaneously preventing global warming. It’s been an either/or choice for quite a while as the narrative of alarmists creates the false dichotomy. Find a third way that doesn’t hurt the environment while still allowing for real human growth, not restraint, and I’ll get on board.

I don’t see how this ISN’T simply the same as saying “Well of course the science is still SETTLED! While it’s true that we didn’t really see this, er, “hiatus” coming, looking back it all makes perfect sense to US, and now that we’ve explained why our prediction didn’t work out you dreary little people should STOP doubting us and get on with living your pathetic lives the way that we say you should.”
I mean, that seems to be precisely the state of the science at the moment: covering itself with a fig leaf and deriding anyone who dares question it.
There are tremendous credibility problems here, and you people who are so adamant that AGW science is settled had better realize that the elitist rhetoric weakens your position, making you seem wedded to ideology rather than objectivity.

This article demonstrates exactly what is wrong with the AGW promoters, when the models that have been touted to be accurate in their ability to predict future climate fail, someone comes up with a theory to accurately predict the past error and that makes everything OK. Well it doesn’t, hind casting is easy. There can be a number of theories that can be used to explain the recent temperature drop/stagnation, the low solar cycle, PDO, LaNina etc. The problem is as far as predicting the future goes the present climate models fail miserably. If the models are any good they should be able to predict the planet temperature distribution for next year, heck even next month. But they can’t, yet we are supposed to believe they can predict the temperature 50 or 100 years from now.

Climate science is one of the few professions where there is no consequence for being wrong. If you are a medical doctor how long do you think you would last if your diagnoses were less then 50% accurate. Or an engineer , gee I’m sorry the plain crashed I’ll do better on that wing design next time.

When climate science can accurately predict the future instead of just the past it will be time to listen to what they have to say. But until then it is unwise and potentially damaging to put any policies in place based on their predictions.

Any “The Earth is cooling” claim that starts of with the phrase “since 1998″ is immediately in the realm of cherry-picking.
If you are so concerned that the warmng has slowed then start your trend from 1997 – or 1996 – or 1999 – or any other year apart from the freak outlier super- El Nino year of 1998 and you will have your warming. Which is of course exactly why the “skeptics” always loce to start with 1998 from the HadCRU data set. All the other data sets have 2005 or 2010 as the warmest year and all data sets show continued warming at 95%+ significance.
Fact.
By the way – if you care to check Roy Spencers temperature graph at AMSU you will see that TODAY; 11th July 2011, is the hottest July 11th since records began.
This means about as much as the old meme “since 1998″ of course but it does make the claim that “the Earth is cooling” look more ridiculous than ever.

#7 touched on this. But having to come up with new explanations makes you guys (not personally, but the AGW types) as prognosticators on CNBC, trying to explain every twist and turn of either the market or a stock. When you listen, it always sort of makes sense (as you do) but when applied to science makes it look like voodoo. Having done science I fully understand that this is the normal ferment and is ultimately good but this public heralding of each small item – not fully vetted as yet – is a bit much.

Notice anything missing here? Another option is “Do they have a point?” If you are not willing to listen, you can never persuade. For instance, like Naomi Oreskes, I hold that models can never “prove” anything.

I never thought I’d see a Warmist admit the earth stopped warming, thank you.

I really hope that Chris and the rest of the Intersection bloggers take time to realize that the deniers have always been right, and the alarmists have always been wrong.

Deniers have been saying for years that a dampening mechanism will blunt the supposed C02 forcing. Now we find that we were exactly right, that the same mechanism that produced the warming, is now producing cooling.

How long will the cooling last before the Warmists give up and admit their ignorance?